Today, the use of presence is starting to become more pervasive in communication systems. For example, Instant Messaging and some web sites use a presence state of the user to indicate if a user is online or offline. This use of presence is convenient to know if someone is online and if they can be contacted. Some systems go even further to identify if someone is present based on their calendar.
However, these limited uses of presence may cause problems based what specifically the person is doing or their role within an activity. For example, if the user's calendar indicates that he is on a conference call, the presence state will indicate that the user is busy. The problem is that the user may wish to be contacted during the conference call; this is because the user's role or activity within the conference may allow contact from others. What is needed is a system that takes into consideration the roles and activities of a user to further define their presence state.